Electricity meters are commonly used by electrical utilities to measure the flow of, for example, electrical power quantities between the power source and customer loads. Within each meter there is a disk which acts as the rotor of a small electric motor coupled to the power line being measured and rotates at a speed proportional to power flowing through the meter.
The amount of power applied to or obtained from a load is accumulated by a register that is coupled mechanically to the disk. The register is read periodically by the utility for customer billing. To enable the utility to determine by inspection whether the meter is operative, whether power is flowing and if so, approximately at what rate and in what direction, a portion of the disk is exposed to be viewed from outside the meter.
Recently developed, microprocessor controlled meters currently becoming adopted by the electrical utilities, have capabilities to carry out numerous metering functions such as demand and time of use measurement within a single meter. One difficulty that has become apparent with such meters, however, is the inability of the meter to provide by visual inspection an indication to the utility of the direction and approximate magnitude of power flow with respect to a load as is possible in the conventional electromechanical electricity meter by simply observing the rotation of the disk.
There accordingly exists a need to provide, in a solid state electricity meter, a visual display to indicate to the utility, and possibly to the customer, the direction and approximate magnitude of power flowing in the lines being measured. A need further exists in such meters to enable the display to provide to the utility the range of power flowing in the line being monitored.